This application is related to the subject matter of commonly owned, co-pending application Ser. No. 10/677,178, filed on even date herewith, the specification of which is incorporated herein by reference.
The invention relates to a test apparatus with loading device, which has a chuck which has a bearing surface for a test substrate, comprising a substrate carrier and component which is to be tested, and is provided with a chuck drive. The chuck can be displaced within a working area by means of the chuck drive. Furthermore, there is a receiving member for receiving test substrates, which can be displaced from a first position within a working area of the chuck to a second receiving position outside the working area.
Test substrates comprise a substrate carrier, on which components which are to be tested are arranged. Components of this type may be semiconductor chips. If these semiconductor chips are tested while they are still on the semiconductor wafer, i.e. while they are still joined to the wafer, the semiconductor wafer itself forms the substrate carrier. However, test substrates may also be other components, such as individual semiconductor chips, hybrid components, micromechanical components and the like. In this case, the test substrates are arranged on the substrate carrier during testing. Each substrate carrier has a smooth and planar underside for resting on the bearing surface of the chuck.
To test test substrates, such as for example semiconductor chips which are still joined to semiconductor wafers, i.e. to test the operational reliability of the semiconductor chips, the latter are brought into contact with contact-making needles, then electrical signals are applied to them via these contact-making needles and the electrical reaction is measured. In this context, it is also possible to test for the optical reaction of the semiconductor chips to the electrical signals or the electrical reaction of the semiconductor chips to the application of light or other radiation. Testing of this type is carried out in a test apparatus, in which the semiconductor wafers are placed onto a wafer receiver, known as a chuck, and are held on the latter. The chuck is located on an X-Y table, so that the semiconductor wafer can be positioned relative to the contact-making needles.
Test apparatus are used to test substrates under different environmental conditions. To produce these environmental conditions, the chuck is surrounded by a housing, inside which it can move freely. This housing allows a controlled atmosphere to be established. The housing can also be used to provide a shield from undesired electromagnetic radiation.
The chuck is used not only to receive the test substrates but also to perform several further functions, such as heating or cooling of the test substrates or the setting of a controlled potential. For this purpose, the chuck is provided with media lines for external connection to corresponding media sources.
Whatever configuration of test apparatus is selected, the chuck has to be provided with a test substrate, i.e. has to be loaded, before testing is carried out. Loading devices are used for this purpose. A loading device is known for use on a test apparatus produced by Cascade Microtec Inc., in which a guide carriage, by means of which the chuck can be detached from the X-Y table and moved out of the housing, is provided on the X-Y table. For this purpose, a flap which allows the chuck to move out is provided in the housing.
For loading purposes, the chuck is moved out of the housing on the guide carriage, through the flap, so that it moves to a receiving position. The receiving position is located on a side of the test apparatus on which an operator usually stands. In this receiving position, a semiconductor wafer is placed onto the chuck by means of forceps. Then, the chuck is moved back in until it has returned to its position above the X-Y table, before then being displaced with the X-Y table for positioning of the contact-making needles. After the chuck has been moved into the housing, the flap is closed again. In this solution, the chuck itself forms the receiving means which is moved from the working area of the chuck into the receiving position. In this case, it should be noted that before the chuck is moved out to the receiving position, it adopts a position within its working area which is closest to the receiving position, in order to keep the displacement distances as short as possible.
A first drawback of this solution is that the chuck has to cover relatively long displacement paths. In this case, all the media lines have to follow this long movement of the chuck and themselves have to be made relatively long. In particular refrigerant lines are relatively rigid and therefore impede the movement of the chuck out of the housing and also the movement of the chuck on the X-Y table. This adversely affects the accuracy of the movement.
A second drawback is that it has to be possible to detach the chuck from the X-Y table, since this entails additional instability and therefore inaccuracies.
A third drawback is that in this solution the chuck has to be moved out of the housing even in situations in which it has to perform cooling functions. In the process, it is then exposed to the open ambient atmosphere, from which moisture will precipitate on the cold chuck, leading to an extremely undesirable introduction of moisture into the housing.
The invention is therefore based on the object of increasing the accuracy of the movement of the chuck. Moreover, in the case of test apparatus with a controlled atmosphere, a further object is to prevent the chuck from being exposed to the open-air atmosphere.